Question:
Write the chemical symbols of the following:
(i) Gold
(ii) Iron
(iii) Chlorine
(iv) Mercury
Answer:
(i) Gold - Au
(ii) Iron - Fe
(iii) Chlorine - Cl
(iv) Mercury - Hg
Atoms and Molecules
Q 1.
Fill in the blanks:
The atomic mass of sodium is 23. The gram atomic mass of sodium is _________.
Q 2.
What is gram-atomic mass of an element?
Q 3.
Fill in the blanks:
According to law of definite proportions, in a chemical substance the elements are always present in __________ proportions by mass.
Q 4.
Define 'formula mass' of a compound.
Q 5.
What is the mass of 5 moles of sodium carbonate (Na
) ?(Atomic masses : Na = 23 u ; C = 12 u ; O = 16 u)
Q 6.
If one mole of carbon atoms weighs 12 gram, what is the mass (in gram) of 1 atom of carbon?
Q 7.
What are the postulates of Dalton's atomic theory?
Q 8.
Which of the following statements is NOT true about an atom?
(a) Atoms are the building blocks from which molecules and ions are formed.
(b) Atoms cannot exist independently.
(c) Atoms are neutral in nature
(d) Atoms combine together to form matter that we can see, feel or touch.
Q 9.
Give four examples of diatomic molecules.
Q 10.
Who proposed Law of Definite Proportions (or Law of Constant Composition)?
Q 11.
Hydrogen and oxygen combine in the ratio of 1:8 by mass to form water. What mass of oxygen gas would be required to react completely with 3 g of hydrogen gas?
Q 12.
Fill in the blanks:
Atomic radius is measured in __________.
Q 13.
What are polyatomic ions? Give examples?
Q 14.
How many atoms are there in 0.25 mole of hydrogen ?
Q 15.
Dalton's atomic theory says that atoms are indivisible. Is this statement still valid ? Give reasons for answer.
Q 16.
Fill in the blanks:
The mass of 1 mole of a substance is called its _____________.
Q 17.
What is the chemical symbol for iron?
Q 18.
Write the chemical symbols of the following:
(i) Gold
(ii) Iron
(iii) Chlorine
(iv) Mercury
Q 19.
What is relative atomic mass of an element? How it is related to atomic mass unit?
Q 20.
Fill in the blanks:
According to Dalton's atomic theory, atoms of different elements differ in ______, size and chemical properties.
Q 21.
Give the names of the elements present in the following compounds.
(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder
(d) Potassium sulphate.
Q 22.
What are ionic compounds?
Q 23.
Fill in the blanks:
Atoms can be observed using ____________ Microscope.
Q 24.
Write down the formulae of
(i) sodium oxide
(ii) aluminium chloride
(iii) sodium suphide
(iv) magnesium hydroxide
Q 25.
Define mole. What is its significance?
Q 26.
What are the building blocks of matter ?
Q 27.
Calculate the number of molecules in 4 g of oxygen.
Q 28.
Calculate the mass in grams of 0.17 mole of hydrogen sulphide, H
Q 29.
(a) What is meant by 'a mole of carbon atoms' ?
(b)(b) Which has more atoms, 50 g of aluminium or 50 g of iron ? Illustrate your answer with the help of calculations.
(Atomic masses : A1 = 27 u ; Fe = 56 u)
Q 30.
What is the law of conservation of mass?
Q 31.
(i) State the law of constant proportions.
(ii) Show that water illustrates the law of constant proportions.
Q 32.
Fill in the blanks:
The chemical symbol of flourine is ________.
Q 34.
Find out number of atoms in 15 moles of He.
Q 35.
'If 100 grams of calcium carbonate (whether in the form of marble or chalk) are decomposed completely,then 56 grams of calcium oxide and 44 grams of carbon dioxide are obtained'.Which law of chemical combination is illustrated by this statement ?
Q 36.
What is meant by atomicity ? Explain with two
Q 37.
Calculate the molecular masses of the following compounds :
(a) Methanol, CH
Q 38.
Write down the formulae for the following compounds :
(a) Calcium oxide
(b) Magnesium hydroxide
Q 39.
An element X has a valency of 4 whereas another element Y has a valency of 1. What will be the formula of the compound formed between X and Y ?
Q 40.
What is the difference between a cation and an anion ? Explain with examples. Using this information, write down the formulae of:
(i) Sodium sulphide
(ii) Copper nitrate
Q 41.
Calculate the mole ratio of 240 g of calcium and 240 g of magnesium. (Ca = 40 u ; Mg = 24 u)
Q 42.
Fill in the blanks:
_________ are building block of all matter.
Q 43.
Can atoms of an element exist independently? Give examples of elements which exist in atomic form. Give examples of elements that do not exist in atomic form.
Q 44.
Based on atomicity, how molecules are categorized?
Q 45.
What is valency of an element?
Q 46.
Who introduced the term 'mole' in chemistry?
Q 47.
How many moles are there in 4.6 gms of Sodium(Na)?
Q 48.
What is meant by the symbol of an element ? Explain with examples.
Q 49.
What do we call those particles which are formed :
(a)by the gain of electrons by atoms ?
(b)by the loss of electrons by atoms ?
Q 50.
State whether the following statements are true or false :
(a)A sodium ion has positive charge because it has more protons than a neutral atom
(b)A chloride ion has negative charge because it has more electrons than a neutral atom.
